Re: I'm working on my last chip in chapter/week 3: the PC chip

Posted by ouverson on Jul 23, 2019; 8:59pm
URL: http://nand2tetris-questions-and-answers-forum.52.s1.nabble.com/I-m-working-on-my-last-chip-in-chapter-week-3-the-PC-chip-tp4033386p4033420.html

I had to look at this for a while and read and reread your "What would happen if ..." until I could "see" the answer.

sel[0] ---> 1 NOT, 1 AND and 1 OR
When reset==1 then sel[0]=1, when reset==0 then sel[0]=0 other than when load==0 and inc==1; in that one case, reset==1 "covers".

This is curious work; I'm always trying to find the method, the procedure to accomplish a task; more often than not what helps me solve the problem at hand is "living with" the parts and pieces for a bit; letting it absorb; waiting for the pattern to appear. Reminds me of those pictures that were popular a decade or so back: the ones you'd stare at for a few minutes until the brain could "see" the image within the image.

Take this implementation of the sel[0] input; I'm not sure I would have "seen it" unless you would have nudged here and hinted there: from my Mux8Way, to my larger canonical expressions, to the sel[1] being a simple OR gate (I should have seen that one!) to this last one which (in my humble opinion) wasn't that obvious.

Thanks so much for your help.